The present invention relates to an apparatus for detecting the surface flaws of a red-hot (hereinafter red-heated) metal part.
The flaws on the surface of the metal part, such as a slab or bloom must be removed before the metal part is fed to the succeeding step. When the moving metal part in a red-hot heated condition has flaws on the surface, it is impossible to detect them by the naked eye in a normal surrounding illumination. Therefor, to detect the flaws on the red-hot heated metal part by the naked eye, the metal part must be cooled to be at a normal temperature condition. By contrast, if the flaw or its condition such as size or depth may be detected under the red-heated condition, the following many advantages may be enjoyed. By executing the flaw detection preceeding the hot scarfer immediately after the metal part is rolled, the necessary steps of the flaw removal for presence, size and position of the flaw may be taken for each steel part. This eliminates yield deterioration due to excessive application of the hot scarf and the need of another flaw removal work operation due to insufficient application of the hot scarf.
Further, the flaw detection is permitted immediately after cogging roll or the hot scarf is rolled. Accordingly, the flaws detected may be partly remedied by the hot rolling, with the metal part in its red-heated state. This permits the use of a direct rolling method in which the red-heated metal part is rolled by the rolling mill at the succeeding step not by way of the furnace and a hot metal part entering method in which the red-heated metal part enters the furnace. The thermal energy loss due to successive cooling and heating of the metal part is relieved. In this case, if the hot partial flow removal should be impossible, it is checked from the condition of the surface flaw of each metal steel part whether the use of the direct rolling method or the hot metal part entering method is proper or not. If the use of such method is improper, the metal part is transferred to the cooling and flaw removal process. On the other hand, if such is proper, the metal part is processed by the method of which the use is proper. In this way, the thermal energy loss may be allleviated also in this case.